This invention relates to a standards converter for allowing a mobile telephone which communicates on a first mobile telephony standard to interface with a base unit which communicates on a second mobile telephony standard. More particularly, this invention relates to a converter that allows a mobile telephone that operates at PCS frequencies to interface with a base unit that operates at cellular telephone frequencies.
Different mobile telephone standards are currently in use. Mobile telephones communicate with base stations in a full-duplex mode in which each channel uses two different frequencies so that each mobile telephone can transmit to the base station and receive from the base station at the same time. This is important because all control of any telephone call is accomplished by the base station, so that even when a user is transmitting, the base station must be able to send control information to the mobile telephone (e.g., if the telephone is in motion, the base station must be able to instruct the telephone to change channels as it is handed off to another base station). Under the standard (as used herein, the term "standard" refers to the agreed-upon frequencies at which a system operates, and not to other "standards" such as those that govern how speech is encoded, etc.) for one type of mobile telephone system known as "cellular," each mobile telephone transmits at any one of a number of frequencies between about 824.01 MHz and about 848.97 MHz and receives at any one of a number of frequencies between about 869.01 MHz and about 893.97 MHz (the individual frequencies within those bands are separated by about 30 kHz). Under the standard for another type of mobile telephone system known as "PCS" (for "Personal Communications Service"), each mobile telephone transmits at any one of a number of frequencies between about 1850.01 MHz and about 1909.95 MHz and receives at any one of a number of frequencies between about 1930.05 MHz and about 1989.99 MHz.
Base stations for mobile telephone systems are generally manufactured for one standard. Similarly, testing equipment, such as that used to test mobile telephones as they are manufactured or are being repaired, typically is provided for testing mobile telephones under only one standard. In the mobile telephone manufacturing and repair context in particular, this requires mobile telephone manufacturing and repair facilities to have a different testing device for each type of mobile telephone that it manufactures or repairs. And because a mobile telephone base station can operate on only one standard, a mobile telephone service provider who provides service under more than one standard must purchase and maintain a variety of different types of base station equipment for the different standards.
It would be desirable to be able to provide a converter that would allow equipment designed for one mobile telephone standard to be used with mobile telephones designed for a different mobile telephone standard.
It would also be desirable to be able to provide an adapter that would allow testing equipment for one type of mobile telephone to be used to test a different type of mobile telephone.
It would further be desirable to be able to provide an adapter that would allow a base station for one type of mobile telephone to be used with a different type of mobile telephone.